The invention generally relates to a gas turbine blade with a platform and with a profile adjoining the platform. The invention also generally relates to a method for producing a gas turbine blade.
A gas turbine blade is disclosed in DE 26 28 807 A. Such a gas turbine blade is exposed to extremely high temperatures and therefore has to be cooled. The gas turbine blade has a platform serving for delimiting a flow duct, into which the gas turbine blade is installed. The platform has adjoining it, a profile which projects into the flow duct and around which the hot gas flows. The platform, too, is exposed to the hot gas. The platform is cooled using an impact-cooling system including an impact-cooling plate which is arranged on the underside of the platform and out of which cooling air flows onto the underside of the platform via impact-cooling orifices. This cooling air then emerges via film-cooling bores on the top side of the platform and forms a cooling film there.
An object of the invention is to specify a gas turbine blade, in which the platform withstands particularly high temperatures, with a comparatively small amount of cooling air being required. A further object of the invention is to specify a method for producing such a gas turbine blade.
According to the invention, the object directed at a gas turbine blade is achieved, for example, by specifying a gas turbine blade with a platform and with a profile adjoining a platform top side of the platform. The platform preferably includes a flow-on edge and a flow-off edge for a hot gas flowing around the gas turbine blade. Further, the platform preferably includes a slot which extends parallel to the inlet edge. Further, ducts are preferably introduced into the platform, which issue into the slot and which lead through the platform to a platform underside located opposite the platform top side.
The platform is preferably exposed to particularly high temperatures, in particular, at its flow-on (inlet) edge. The flow-on edge is that edge of the platform which is directed counter to the onflowing hot gas. This region of the platform can be cooled only with difficulty, since the profile located in front of it and a rounded and therefore thickened transitional region between the profile and the platform result in a geometry which is difficult to cool. By using the invention, it is now possible, in a simple way in manufacturing terms, to cool the platform flow-on edge efficiently. This is preferably carried out by cooling air being conducted from the platform underside through the ducts into the slot, where it cools the platform efficiently in the inlet-edge region. In this case, the wall formed between the slot and the inlet edge is preferably about 1-3 mm thick. This comparatively thin design results in good coolability, without load-bearing regions being adversely affected.
Preferably, the slot is inclined toward the profile in a direction from the platform underside to the platform top side, in such a way that a cooling fluid emerging from the slot brings about a film cooling of the platform top side. The slot is therefore tilted over its height in a direction from the flow-on (inlet) edge to the flow-off (outlet) edge. The inclination is in this case dimensioned such that cooling fluid, in particular cooling air, emerging under normal operating conditions sweeps along on the platform top side so as to form a film and thus has a film-cooling effect. After the cooling of the flow-on edge of the platform by the cooling fluid, the latter also serves subsequently for a film cooling of the platform top side.
Preferably, the ducts are directed in such a way that they issue into the slot in a direction toward the inlet edge. As a result, the cooling fluid emerging from the ducts is guided in an impact-cooling manner against that wall of the slot which is adjacent to the flow-on edge. This impact cooling gives rise to a particularly efficient cooling of the platform flow-on edge.
The gas turbine blade is preferably designed as a movable blade.
According to the invention, the object directed at a method is achieved, for example, by specifying a method for producing a gas turbine blade with a platform and with a profile adjoining a platform top side of the platform. The platform preferably includes a flow-on edge and a flow-off edge for a hot gas flowing around the gas turbine blade, wherein a slot which extends parallel to the inlet edge is introduced into the platform. Further, ducts are preferably introduced into the platform, which issue into the slot and which lead through the platform to a platform underside located opposite the platform top side.
The advantages of such a method are afforded correspondingly to the statements with regard to the advantages of the gas turbine blade.
The slot is preferably eroded into the platform.
Also preferably, the ducts are introduced into the platform by laser drilling. Preferentially, in this case, a light-scattering guard is mounted on that wall of the slot which is adjacent to the inlet edge prior to the completion of the laser drilling, so that this wall of the slot is not damaged by the laser radiation. More preferably, this light-scattering guard is a Teflon strip. In the particularly material-protecting and efficient manufacture of the ducts by laser drilling, there is initially the risk that, while the ducts are being drilled through, ultimately the wall of the slot which is adjacent to the inlet edge will be damaged by the laser radiation emerging from the ducts at the end of the manufacturing process. This is prevented by the light-scattering guard, in particular the mounting of the Teflon strip constituting a simple and quick method.